Groebke-Blackburn-Bienaymé Reaction for DNA-Encoded Library Technology.

This study presents a DNA-compatible synthesis of diverse 5-arylimidazo[1,2-a]pyridin-3-amine derivatives using the Suzuki-Miyaura reaction, followed by a Groebke-Blackburn-Bienaymé (GBB) reaction. The GBB reaction demonstrates a wide substrate scope, mild one-pot reaction conditions, and compatibility with subsequent enzymatic ligation, highlighting its potential in DNA-encoded library technology.

Recent Development of Aminoacyl-tRNA Synthetase Inhibitors for Human Diseases: A Future Perspective.

Aminoacyl-tRNA synthetases (ARSs) are essential enzymes that ligate amino acids to tRNAs and translate the genetic code during protein synthesis. Their function in pathogen-derived infectious diseases has been well established, which has led to the development of small molecule therapeutics. The applicability of ARS inhibitors for other human diseases, such as fibrosis, has recently been explored in the clinical setting. There are active studies to find small molecule therapeutics for cancers. Studies on central nervous system (CNS) disorders are burgeoning as well. In this regard, we present a concise analysis of the recent development of ARS inhibitors based on small molecules from the discovery research stage to clinical studies as well as a recent patent analysis from the medicinal chemistry point of view.

DNA-Encoded Library Screening as Core Platform Technology in Drug Discovery: Its Synthetic Method Development and Applications in DEL Synthesis.

DNA-encoded library technology (DELT) was introduced to our medicinal chemistry society more than 20 years ago. The application of DELT in the development of clinical candidates has been actively reported in the literature recently. A few representative examples include RIP1K inhibitors for inflammatory diseases and sEH inhibitors for endothelial dysfunction or abnormal tissue repair, among many others. Here, the authors would like to recall the recent developments in on-DNA synthetic methodologies for DEL construction and to analyze recent examples in the literature of DELT-based drug development efforts pursued in both the academic and industrial sectors. With this perspective, we hope to provide a useful summary of recent DELT-based drug discovery research and to discuss the future scope of DELT in medicinal chemistry.

Recent Development of Small Molecule Glutaminase Inhibitors.

Glutaminase (GLS), which is responsible for the conversion of glutamine to glutamate, plays a vital role in up-regulating cell metabolism for tumor cell growth and is considered to be a valuable therapeutic target for cancer treatment. Based on this important function of glutaminase in cancer, several GLS inhibitors have been developed in both academia and industry. Most importantly, Calithera Biosciences Inc. is actively developing the glutaminase inhibitor CB-839 for the treatment of various cancers, and it is currently being evaluated in phase 1 and 2 clinical trials. In this review, recent efforts to develop small molecule glutaminase inhibitors that target glutamine metabolism in both preclinical and clinical studies are discussed. In particular, more emphasis is placed on CB-839 because it is the only small molecule GLS inhibitor being studied in a clinical setting. The inhibition mechanism is also discussed based on X-ray structure studies of thiadiazole derivatives present in glutaminase inhibitor BPTES. Finally, recent medicinal chemistry efforts to develop a new class of GLS inhibitors are described in the hopes of providing useful information for the next generation of GLS inhibitors.

Recent developments in small molecule therapies for renal cell carcinoma.

Renal cell carcinoma (RCC) is the most common type of kidney cancer in adults and is known to be the 10th most common type of cancer in the world. Most of the currently available RCC drugs are tyrosine kinase inhibitors (TKIs). However, combination therapies of TKIs and immune checkpoint inhibitors such as programmed cell death protein 1 (PD-1) and programmed cell death protein 1 ligand 1 (PD-L1) inhibitors are the focus of most of the final stage clinical trials. Meanwhile, other small molecule therapies for RCC that target indoleamine-2,3-dioxygenase (IDO1), glutaminase, C-X-C chemokine receptor 4 (CXCR4), and transglutaminase 2 (TG2) are emerging as the next generation of therapeutics. In this review, these three major streams for the development of small molecule drugs for RCC are described.

Recent Progress in the Development of Transglutaminase 2 (TGase2) Inhibitors.

Transglutaminase 2 (TGase2, TG2) activity has been implicated in the pathogenesis of a number of unrelated disorders, including celiac, neurological, and renal diseases, and various forms of cancer. It has been suggested that TGase2 activity, such as cross-linking, deamidation, and GTP-related activity, is associated with each disease. Continuing efforts to develop small molecule TG2 inhibitors are ongoing. To develop a new class of TG2 inhibitors, the factors impeding the development of TG2 inhibitors have been identified. Additionally, the conformational effect of TG2 enzyme in regard to its pathological roles, in vitro screening methods, recently discovered TG2 inhibitors, and preclinical evaluations are discussed with a brief summary of current TG2 inhibitor pipelines under the clinical setting.

Inter-molecular crosslinking activity is engendered by the dimeric form of transglutaminase 2.

Transglutaminase 2 (TGase 2) catalyzes a crosslink between protein bound-glutamine and -lysine. We proposed the mechanism of TGase 2 activation depends on conformation change from unfolded monomer to unfolded dimer. We found that TGase 2 has temperature-sensitive conformation change system at 30 °C. Small-angle X-ray scattering analysis showed that the enzyme was maintained as an unfolded monomer at temperatures below 30 °C, but changed to an unfolded dimer at over 30 °C. Mass analysis revealed that the C-terminus of TGase 2 was the critical region for dimerization. Furthermore, this conformational switch creates new biochemical reactivity that catalyzed inter-molecular crosslink at above 30 °C as an unfolded dimer of TGase 2 while catalyzed intra-molecular crosslink at below 30 °C as an unfolded monomer of TGase 2. The mechanism of TGase 2 activation depends on temperature-sensitive conformation change from unfolded monomer to unfolded dimer at over 30 °C. Furthermore, inter-molecular crosslinking activity is generated by the dimeric form of TGase 2. TGase 2 switches its conformation from a monomer to a dimer following a change in temperature, which engendered unique catalytic function of enzyme as inter-molecular crosslinking activity with calcium.

Assessment of pharmacokinetics, bioavailability and protein binding of anacetrapib in rats by a simple high-performance liquid chromatography-tandem mass spectrometry method.

Anacetrapib is a potent and selective CETP inhibitor and is undergoing phase III clinical trials for the treatment of dyslipidemia. A simple and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the quantification of anacetrapib in rat plasma was developed and validated using an easily purchasable compound, chlorpropamide, as an internal standard (IS). A minimal volume of rat plasma sample (20 µL) was prepared by a single-step deproteinization procedure with 80 µL of acetonitrile. Chromatographic separation was performed using Kinetex C18 column with a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid at a flow rate of 0.3 mL/min. Mass spectrometric detection was performed using selected reaction monitoring modes at the mass/charge transitions m/z 638 → 283 for anacetrapib and m/z 277 → 175 for IS. The assay was validated to demonstrate the selectivity, linearity, precision, accuracy, recovery, matrix effect and stability. The lower limit of quantification was 5 ng/mL. This LC-MS/MS assay was successfully applied in the rat plasma protein binding and pharmacokinetic studies of anacetrapib. The fraction of unbound anacetrapib was determined to be low (ranging from 5.66 to 12.3%), and the absolute oral bioavailability of anacetrapib was 32.7%.

Cabozantinib for the treatment of non-small cell lung cancer with KIF5B-RET fusion. An example of swift repositioning.

A new chimeric fusion transcript of KIF5B (the kinesin family 5B gene) and the RET (Rearranged during Transcription) oncogene, KIF5B-RET, was found in 1-2% of lung adenocarcinomas (LADCs) in 2012. Several related clinical trials for non-small cell lung cancer (NSCLC) with KIF5B-RET rearrangements using existing RET inhibitors, such as cabozantinib, lenvatinib, vandetanib, sunitinib, ponatinib, and AUY922, have been swiftly initiated by the discovery of the KIF5B-RET fusion gene. Anti-RET activity and the status of clinical development of cabozantinib for KIF5B-RET fusion-positive NSCLC are discussed.

Injectable hydrogels derived from phosphorylated alginic acid calcium complexes.

Phosphorylation of sodium alginate salt (NaAlg) was carried out using H3PO4/P2O5/Et3PO4 followed by acid-base reaction with Ca(OAc)2 to give phosphorylated alginic acid calcium complexes (CaPAlg), as a water dispersible alginic acid derivative. The modified alginate derivatives including phosphorylated alginic acid (PAlg) and CaPAlg were characterized by nuclear magnetic resonance spectroscopy for (1)H, and (31)P nuclei, high resolution inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. CaPAlg hydrogels were prepared simply by mixing CaPAlg solution (2w/v%) with NaAlg solution (2w/v%) in various ratios (2:8, 4:6, 6:4, 8:2) of volume. No additional calcium salts such as CaSO4 or CaCl2 were added externally. The gelation was completed within about 3-40min indicating a high potential of hydrogel delivery by injection in vivo. Their mechanical properties were tested to be ≤6.7kPa for compressive strength at break and about 8.4kPa/mm for elastic modulus. SEM analysis of the CaPAlg hydrogels showed highly porous morphology with interconnected pores of width in the range of 100-800µm. Cell culture results showed that the injectable hydrogels exhibited comparable properties to the pure alginate hydrogel in terms of cytotoxicity and 3D encapsulation of cells for a short time period. The developed injectable hydrogels showed suitable physicochemical and mechanical properties for injection in vivo, and could therefore be beneficial for the field of soft tissue engineering.

Progress in Discovery of KIF5B-RET Kinase Inhibitors for the Treatment of Non-Small-Cell Lung Cancer.

A new chimeric fusion transcript of KIF5B (the kinesin family 5B gene) and the RET (Rearranged during Transcription) oncogene, KIF5B-RET, was found in 1-2% of lung adenocarcinomas (LADCs) in late 2011. Several related clinical trials for non-small-cell lung cancer (NSCLC) with KIF5B-RET rearrangements using existing RET inhibitors, such as lenvatinib, vandetanib, sunitinib, ponatinib, cabozantinib, and AUY922, have been swiftly initiated by the discovery of the KIF5B-RET fusion gene. Anti-RET activity and the status of clinical development of these known RET tyrosine kinase inhibitors (TKIs) for KIF5B-RET fusion-positive NSCLC are discussed. A kinase inhibitor that can target a driver mutation specifically may lead to a superior clinical benefit compared with broad-spectrum kinase inhibitors. In this regard, an analysis of the structure of RET kinase and its complex with known RET inhibitors are also briefly discussed.

NAAG peptidase inhibitor improves motor function and reduces cognitive dysfunction in a model of TBI with secondary hypoxia.

Immediately following traumatic brain injury (TBI) and TBI with hypoxia, there is a rapid and pathophysiological increase in extracellular glutamate, subsequent neuronal damage and ultimately diminished motor and cognitive function. N-acetyl-aspartyl glutamate (NAAG), a prevalent neuropeptide in the CNS, is co-released with glutamate, binds to the presynaptic group II metabotropic glutamate receptor subtype 3 (mGluR3) and suppresses glutamate release. However, the catalytic enzyme glutamate carboxypeptidase II (GCP II) rapidly hydrolyzes NAAG into NAA and glutamate. Inhibition of the GCP II enzyme with NAAG peptidase inhibitors reduces the concentration of glutamate both by increasing the duration of NAAG activity on mGluR3 and by reducing degradation into NAA and glutamate resulting in reduced cell death in models of TBI and TBI with hypoxia. In the following study, rats were administered the NAAG peptidase inhibitor PGI-02776 (10mg/kg) 30 min following TBI combined with a hypoxic second insult. Over the two weeks following injury, PGI-02776-treated rats had significantly improved motor function as measured by increased duration on the rota-rod and a trend toward improved performance on the beam walk. Furthermore, two weeks post-injury, PGI-02776-treated animals had a significant decrease in latency to find the target platform in the Morris water maze as compared to vehicle-treated animals. These findings demonstrate that the application of NAAG peptidase inhibitors can reduce the deleterious motor and cognitive effects of TBI combined with a second hypoxic insult in the weeks following injury.

Cascaded two-photon spectroscopy of Yb atoms with a transportable effusive atomic beam apparatus.

We present a transportable effusive atomic beam apparatus for cascaded two-photon spectroscopy of the dipole-forbidden transition (6s(2)(1)S0↔ 6s7s (1)S0) of Yb atoms. An ohmic-heating effusive oven is designed to have a reservoir volume of 1.6 cm(3) and a high degree of atomic beam collimation angle of 30 mrad. The new atomic beam apparatus allows us to detect the spontaneously cascaded two-photons from the 6s7s(1)S0 state via the intercombination 6s6p(3)P1 state with a high signal-to-noise ratio even at the temperature of 340 °C. This is made possible in our apparatus because of the enhanced atomic beam flux and superior detection solid angle.

NAAG peptidase inhibitor reduces cellular damage in a model of TBI with secondary hypoxia.

Traumatic brain injury (TBI) leads to a rapid and excessive glutamate elevation in the extracellular milieu, resulting in neuronal degeneration and astrocyte damage. Posttraumatic hypoxia is a clinically relevant secondary insult that increases the magnitude and duration of glutamate release following TBI. N-acetyl-aspartyl glutamate (NAAG), a prevalent neuropeptide in the CNS, suppresses presynaptic glutamate release by its action at the mGluR3 (a group II metabotropic glutamate receptor). However, extracellular NAAG is rapidly converted into NAA and glutamate by the catalytic enzyme glutamate carboxypeptidase II (GCPII) reducing presynaptic inhibition. We previously reported that the GCPII inhibitor ZJ-43 and its prodrug di-ester PGI-02776 reduce the deleterious effects of excessive extracellular glutamate when injected systemically within the first 30 min following injury. We now report that PGI-02776 (10mg/kg) is neuroprotective when administered 30 min post-injury in a model of TBI plus 30 min of hypoxia (FiO(2)=11%). 24h following TBI with hypoxia, significant increases in neuronal cell death in the CA1, CA2/3, CA3c, hilus and dentate gyrus were observed in the ipsilateral hippocampus. Additionally, there was a significant reduction in the number of astrocytes in the ipsilateral CA1, CA2/3 and in the CA3c/hilus/dentate gyrus. Administration of PGI-02776 immediately following the cessation of hypoxia significantly reduced neuronal and astrocytic cell death across all regions of the hippocampus. These findings indicate that NAAG peptidase inhibitors administered post-injury can significantly reduce the deleterious effects of TBI combined with a secondary hypoxic insult.

Synthesis of cyclopentenols and cyclopentenones via nickel-catalyzed reductive cycloaddition.

Strategies for the reductive cycloaddition of enals or enoates with alkynes have been developed. The enal-alkyne cycloaddition directly affords cyclopentenols, whereas the enoate-alkyne cycloaddition affords the analogous cyclopentenones. The mechanism of these processes likely involves formation and protonation of a metallacyclic intermediate. The general strategy provides a straightforward entry to five-membered ring products from simple, stable π-systems.

Post-injury administration of NAAG peptidase inhibitor prodrug, PGI-02776, in experimental TBI.

Traumatic brain injury (TBI) leads to a rapid and excessive increase in glutamate concentration in the extracellular milieu, which is strongly associated with excitotoxicity and neuronal degeneration. N-acetylaspartylglutamate (NAAG), a prevalent peptide neurotransmitter in the vertebrate nervous system, is released along with glutamate and suppresses glutamate release by actions at pre-synaptic metabotropic glutamate autoreceptors. Extracellular NAAG is hydrolyzed to N-acetylaspartate and glutamate by peptidase activity. In the present study PGI-02776, a newly designed di-ester prodrug of the urea-based NAAG peptidase inhibitor ZJ-43, was tested for neuroprotective potential when administered intraperitoneally 30 min after lateral fluid percussion TBI in the rat. Stereological quantification of hippocampal CA2-3 degenerating neurons at 24 h post injury revealed that 10 mg/kg PGI-02776 significantly decreased the number of degenerating neurons (p<0.05). Both average latency analysis of Morris water maze performance and assessment of 24-hour memory retention revealed significant differences between sham-TBI and TBI-saline. In contrast, no significant difference was found between sham-TBI and PGI-02776 treated groups in either analysis indicating an improvement in cognitive performance with PGI-02776 treatment. Histological analysis on day 16 post-injury revealed significant cell death in injured animals regardless of treatment. In vitro NAAG peptidase inhibition studies demonstrated that the parent compound (ZJ-43) exhibited potent inhibitory activity while the mono-ester (PGI-02749) and di-ester (PGI-02776) prodrug compounds exhibited moderate and weak levels of inhibitory activity, respectively. Pharmacokinetic assays in uninjured animals found that the di-ester (PGI-02776) crossed the blood-brain barrier. PGI-02776 was also readily hydrolyzed to both the mono-ester (PGI-02749) and the parent compound (ZJ-43) in both blood and brain. Overall, these findings suggest that post-injury treatment with the ZJ-43 prodrug PGI-02776 reduces both acute neuronal pathology and longer term cognitive deficits associated with TBI.

Total synthesis of (5R,6R,8R,9S)-(-)-5,9Z-indolizidine 221T using sulfinimine-derived N-sulfinyl beta-amino ketones.

The first total asymmetric synthesis of the poison frog alkaloid (-)-221T, a 5,6,8-trisubstituted indolizidine is described. The key core piperidine ring was constructed via an acid catalyzed intramolecular cascade Mannich cyclization reaction of a N-sulfinyl syn-alpha-methyl beta-amino ketone and crotonaldehyde. The beta-amino ketone was prepared via the reaction of prochiral lithium Weinreb amide enolate with an enantiopure N-2,4,6-triisopropylphenylsulfinyl imine.

Vinylaluminum addition to sulfinimines (N-sulfinyl imines). Asymmetric synthesis of anti-alpha-alkyl beta-amino esters.

Addition of vinylaluminum NMO reagents to N-(p-toluenesufinyl)- and N-(2-methypropanesulfinyl)-derived sulfinimines gives N-sulfinyl aza-Morita-Baylis-Hillman products (dr = 7:1 to 12:1) that result from addition of the reagent from the least hindered direction. Hydrogenation of the aza-MBH adducts with a Rh(I) catalyst affords anti-alpha-substituted N-sulfinyl-beta-amino esters in good yield and high dr (10:1 to 21:1).